The present invention relates to an infinitely variable transmission provided with a belt driven pulley device.
Although, in an infinitely belt-drive variable transmission for a vehicle, the transmission ratio is continuously changed, a selector device for changing the transmission to forward drive state, reverse drive state, or neutral state must be provided. U.S. Pat. No. 4,304,150 discloses an infinitely variable belt-drive transmission provided with a selector device at the output shaft of the transmission. The selector device comprises a selector sleeve forming part of a double dog clutch. In order to engage the dog clutch with a corresponding wheel, the engine must be stopped or double-clutching must be done during the driving of the vehicle. This is troublesome operation. However, it is impossible to provide a synchromesh mechanism in the selector device, since the infinitely variable transmission as a synchronized member has a great inertial mass.
Japanese Patent Laid Open No. 57-129955 discloses a selector device comprising a planetary gear device and an hydraulic clutch, which is provided at the input shaft of the transmission. However, the device is very complicated in construction and is expensive. In addition, the length of the engine including the transmission becomes very large, which is disadvantageous for mounting the transmission on a vehicle.